含SVG的新能源多馈入系统振荡分析和广义短路比计算

弱电网中静止无功发生器(SVG)与新能源设备交互作用明显,如何分析含SVG的新能源多馈入系统的振荡特征是个难题.为此,建立了SVG和新能源联合运行且网络结构保持的系统动态模型,提出了考虑SVG影响的新能源多馈入系统广义短路比计算方法,并用于判断系统是否稳定以及量化系统稳定裕度.首先,推导了网络结构保持的模型的系统传递函数矩阵和特征方程;然后,基于模态摄动理论构造了可近似多馈入系统主导特性的等效同构多馈入系统,并严格论证广义短路比可用于分析含SVG的新能源多馈入系统的振荡稳定裕度;最后,给出了考虑SVG影响的新能源多馈入系统广义短路比及其临界值计算方法,以及电网强度和系统振荡稳定裕度的量化方法.仿真算例说明了所提分析和计算方法的有效性.

Analysis on Oscillation of Multi-infeed System with Renewable Energy and Static Var Generator and Calculation of Its Generalized Short-circuit Ratio

The interaction between static var generator (SVG) and renewable energy equipment becomes obvious in weak grids, and it is a difficult problem to analyze the oscillation characteristics of multi-infeed system with renewable energy and SVGs. To deal with this issue, a system dynamic model with unified operation of SVG and renewable energy which can preserve the network structure is established. Also, a generalized short-circuit ratio calculation method for multi-infeed system with renewable energy considering SVG effect is proposed to judge whether the system is stable and to quantify the stability margin of the system. Firstly, the system transfer function matrix and characteristic equation of the network structure preserving model are derived. Then, based on the modal perturbation theory, an equivalent homogeneous multi-infeed system which approximates the dominant characteristics of the system is constructed. And it is strictly proved that the generalized short-circuit ratio can be used to analyze the oscillation stability margin of multi-infeed system with renewable energy and SVGs. Finally, the calculation method of generalized short-circuit ratio and its critical value in multi-infeed system with renewable energy considering SVG effect is given. Besides, the quantitative method of the power grid strength and system oscillation stability margin is presented. The simulation results verify the validity of the proposed analysis and calculation method.